Cartridges used in image forming devices include toner to form an image on a media sheet. A number of different sensing mechanisms have been used for detecting the amount of toner remaining within the cartridge. One detection method includes detecting the amount of torque applied to an agitating member that rotates through the toner. The torque on the agitating member can be sensed to determine the remaining amount of toner.
Another method includes optical detecting using an optical sensor that radiates a light beam through a transparent window in the cartridge. In one embodiment, an emitter directs a light beam through an opening in the cartridge. The light beam reflects off a surface within the cartridge and is detected by a sensor positioned next to the emitter. The amount of reflected light determines the remaining amount of toner. In another embodiment, a second opening is positioned in the cartridge opposite from the first opening. The sensor is positioned at the second opening to receive the light beam directly from the emitter. Again, the amount of detected light determines the remaining amount of toner.
The cartridge may be used in the image forming device until the toner is exhausted. The cartridge is then removed from the device and replaced with a new cartridge. The exhausted cartridge is then either discarded, or refilled with new toner. The cartridge should have some manner of gaining access to the interior to allow for new toner to be refilled and used again within the image forming device. The refilling mechanism should provide a durable seal to prevent toner from leaking during the image formation process. The access point should also be positioned at a location on the cartridge to not interfere with the other cartridge mechanisms.